Manufacture of crucible-steel.



UNITED STATES PATENT OFFICE.

EBEN B. CLARKE, OF PITTSBURG, PENNSYLVANIA, ASSIGNOR TO FIRTH STERLINGSTEEL COMPANY, A CORPORATION OF PENNSYLVANIA.

MANUFACTURE OF CRUClBLE-STEEL.

SPECIFICATION forming part of Letters Patent No. 703,543, dated July 1,1902.

Application filed March 30, 1901.

. To all whom it may concern:

Beit known that I, EBENB. CLARKE, of No; 4629 Bayard street, in the cityof Pittsburg, State of Pennsylvania, have invented certain new anduseful Improvements in the Mannfacture of Crucible-Steel, of which thefollowing is a specification.

The objects. of the invention are to reduce the cost of manufacture andalso to improve the composition of the steel by enabling it to be mademore uniformly.

The invention accomplishes a great saving in the time required fortreatment of the materials in the crucible, a great increase in the lifeof the crucibles, an increased capacity by reason of a greater quantityof steel being made in each crucible at each charge, and the productionof a more uniform composition of crucible-steel at a decreased cost.

One of the usual processes of making crucible-steel is to introduce intothe crucible pieces of bar-iron or bar-steel and scrap-iron orscrap-steel of the same or various degrees of carbonization with carboneither combined with some metal, as iron, or in a non-metallic shape,such as charcoal, together with such other modifying substances as maybe desired. The crucible filled with these materials in a cold state isthen covered with the usual cover and placed in the crucible-furnace,where it remains for several hours until the contents are melted andtime is given for the completion of the reactions which take place inthe formation of crucible-steel, the time depending on the size andcharacter of the crucible, the fusibility of the material contained, andother well-known conditions. Another method is to use blister-bar orother iron or steel of high carbon and introduce this with quantities ofiron, steel, or scrap of carbonization requisite to finally give thedesired degree of carbonization within the crucible at the end of theprocess. I believe it has been proposed to make a so-calledcrucible-steel by subjecting the raw materials to a preliminarytreatment in a Martin furnace or converter, whereby its carbon isreduced to the necessary quantity and it is freed from manganese,-sulfur, and phosphorous or other impurities. This process is es- SerialNo. 53 ,681. (No specimens.)

sentially diiferent from a true crucible process, because itcontemplates metallurgical treatment prior to the introduction of thesteel into the crucible.

The improvement which forms the subjectmatter of the present inventionconsists in introducing the usual ingredients of cruciblesteel into thecrucible while they or most of them are in a heated state. Preferablythe raw material in the form of iron or steel bars and scrap of variousdegrees of carbonization is first melted in quantities sufficient tocharge a number of crucibles and is then introduced intocrucibles,preferably already heated, into which the necessary amount ofcarbon, with or without other modifying substances-such as manganese,&c.is also introduced, if such addition of carbon or other modifyingsubstances are necessary to perfect the composition of the fi nishedcrucible-steel. The cover is then placed on the crucible, and thecrucible is subjected to continuous heating in the crucible-furnace forsuch a time as is necessary to complete the formation of thecrucible-steel. In this way a much more uniform composition of materialcan be obtained with much less care than where the materials are chargedin a cold state into each separate crucible. The addition of carbon orcarbonizin g substance or other modifying substances if introduced intothe crucible form at most but a small part of the crucible-steel and maytherefore be introducod in a cold state as more convenient. If desired,the heating or fusing of the raw material can take place on a muchlarger scale by a continuous process analogous to the Talbot process ofmanufacturing open-hearth steel.

By this improved process the time and heat required to raise the rawmaterials to the melting temperature and to supply the latent heatrequired to melt them are entirely saved so far as the crucible-furnaceis concerned. The life of the crucible is thereby prolonged.Furthermore, no waste of heat occurs in the preliminary heating of thecrucible, because as soon as one lot of finished steel has been pouredout from a crucible that same crucible in its highly-heated state isready to receive the new charge. The time necessary to heat the crucibleis therefore saved and the utility or life of the crucible therebyfurther augmented.

There is obviously a great saving in labor and increased capacity of theplant.

I am aware that it has been proposed to make crucible-steel frompig-iron and other materials by first making either Bessemer oropenhearth steel and immediately upon the steel reaching the supposedlyproper conditions tapping it 01f into crucibles for its final treatment.Such processes are dependent upon the estimation of the right moment atwhich to tap ofi, because the metal is undergoing a continuingmetallurgical treatment or reaction and its proportions are changing aslong as it remains in the converter or in the open hearth. My processfurnishes a means of producing crucible-steel of uniform andpredetermined composition in a more economical manner than heretofore,and yet with all the exactness of proportions necessary to highgradecrucible steel. The materials are brought together in known andaccuratelydetermined proportions, and instead of undergoing changes inproportion during the melting process they may and always should becarefully protected as far as possible from any oxidation or change bycovering, as is well understood in the art, with a neutral or inactiveslag. Therefore my process is practically independent of the precisemoment chosen for pouring the molten metal into the crucible, and it isalso independent of the uncertainty and lack of uniformitycharacterizing successive heats of open-hearth steel even when made inthe same hearth and by the same maker.

I claim as my improvement and desire to secure by Letters Patent thefollowing:

1. The improved process of making crucible-steel, which consists infirst introducing the materials for making crucible-steel in therequired predetermined proportions into a receptacle and melting them,in contradistinction to treating the materials with oxidizing ormetallurgical agents, whereby change in the proportions may be avoided,and then introducing the melted mass into a previouslyheated cruciblewith carbon or other modifying substance and covering the crucible, andsubjecting it to further heating for a limited time, substantially forthe purposes described.

2. The improved process of making crucible-steel, which consists infirst introducing the raw materials of steel or iron, or the like, inthe cold state and in predetermined proportions into a suitableheating-receptacle and melting them without Bessemer or openhearthreactions, and then immediately without other metallurgical treatmentand before the formation of the finished crucible-steel takes place,introducing the melted mass into a crucible and closing the same, andsubjecting the crucible and its contents to a continued heating whilethe crucible-steel is being produced therein, substantially for thepurposes described.

3. The improvement in crucible-steel processes which consists in meltingtogether the greater portions, at least, of the crucible-steelingredients in predetermined proportions and without causing substantialchange of proportions by chemical or metallurgical treatment, andthereafter introducing said ingredients into a crucible, covering themto protect them from oxidation, and thereafter-subjecting them to heatduring a limited time, substantially for the purposes described.

Signed this 25th day of March, 1901, at Pittsburg, Pennsylvania.

EBEN B. CLARKE.

Witnesses:

T. DAVID MoCLosKEY, BERTHA TROTH.

